This is another chunk of the opal from Eden Valley, specifically, the Blue Forest. Both this piece and the one in question came from the same area on the same trip. The crystal druzy on the top is calcite.
Another piece of blue opal from the same trip.
This is a piece from the same area but a different trip that I have polished on the ends to show off the swirling of the wood and the opal.
I don’t know if these can help identify my mystery rock, but it should help rule out a few possibilities.
RE: What is this rock?